Details can be found in the Qualys advisory at
https://https://www.qualys.com/2021/05/04/21nails/21nails.txt
For the stable distribution (buster), these problems have been fixed in
version 4.92-8+deb10u6.
We recommend that you upgrade your exim4 packages.
For the detailed security status of exim4 please refer to its security
tracker page at:
https://security-tracker.debian.org/tracker/source-package/exim4
Further information about Debian Security Advisories, how to apply
these updates to your system and frequently asked questions can be
found at: https://www.debian.org/security/
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